The invention relates to a nozzle device for discharging viscous materials, particularly adhesive or sealing materials, onto a surface in ribbon form. The device includes a cylinder-shaped inside part having an axial bore into which the material is introduced at a first or input end of the device and discharged by an axial nozzle bore at a second or discharge end of the device. The device further has a cylinder-shaped outside part that coaxially and in a spaced manner surrounds the inside part to form an annular space. The nozzle device also has a feed port extending radially through the wall of the outside part into the annular space to supply a gas, especially air, and a cap to be screwed onto the outside part at the end of the nozzle device. Further, a coaxial discharge bore is provided, having an internal cylinder-shaped bore segment, an adjacent, conically tapering surface and an outer, cylindrical bore segment adjoining the conical surface.
U.S. Pat. No. 5,421,490 shows and describes a nozzle device of the above-noted type where axially parallel channels are formed on the outer circumference of the inside part, so that the annular space between the inside and outside parts is divided into individual channels by axially parallel separating walls. According to the patent, a particularly uniform ribbon cross-section can be achieved in this way. Such a solution is sought to provide an improvement over a previously known method, described, for example, in U.S. Pat. No. 4,995,333. According to this method, helical rather than axially parallel gas channels are provided, so that the gas jets helically impinge on the discharged material string. Under certain conditions this causes the material string to be deflected continuously in a circular motion, so that the material is deposited in the form of a ribbon, composed of a plurality of overlapping circles. To be sure, this method of string forming is criticized in the earlier noted U.S. Pat. No. 5,421,490 because necessarily more material reaches the edge regions than the center region of the developing string. Such an irregularity, however, is frequently accepted in practice, especially since a certain deformation and adaptation of the material string occurs, for example, when adhesive or sealing materials are applied, as a result of the subsequent pressing together of two parts to be connected.
It is a disadvantage of the two known solutions that the gas, especially air, must be driven through relatively narrow channels toward the nozzle opening, thereby limiting the possible amount of air. On the other hand, the possible amount of air itself determines the possible material flow quantity and thus also determines the processing speed. Since, however, an increasing material viscosity requires a higher amount of air to form the material string, the limiting of the air amount unfavorably affects the delivery speed, especially for highly viscous materials.
On the other hand, a gun for applying an asphalt-type material is known, for example, from U.S. Pat. No. 1,989,696, for example, where the annular space between the inside part and the outside part is completely unobstructed so that a large amount of gas can be supplied. In that case, however, the inner tube is not supported such that it is positioned in a precise and centered manner inside the outer tube.